Nonregenerative catalytic reforming process



Oct. 6, 1953 c. v. BERGER ET AL 2,654,694

NONREGENERATIVE CATALYTIC REFORMI NG PROCESS Filed Oct. 17, 1951 uaddliis HOiVUVdQS INVENTORS CHARLES V. BERGER DAVID D. HANSEN BY: cm; 2%;

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ATTORNEYS:

Patented Oct. 6, 1953 2,654,694 N ON RE GEN ERATIV E CATALYTIC REFORMIN Charles V. Berger, David D. Hansen,

' Universal Oil Products a corporation of Delawa G PROCESS Western Springs, 111., and Shreveport, La., assignors to Company, Chicago, 11]., re

Application October 17, 1951, Serial No. 251,668

Claims.

This application is a continuation-in-part of our previously filed copending application relating to a hydrocarbon conversion process, Serial No. 34,974, filed June 24, 1948, now abandoned.

This invention relates to the endothermic conversion of substantially olefin-free hydrocarbon fractions containing naphthenes and/or paraffins and boiling approximately within the gasoline It is more specifically concerned with a particular method of reforming straight-run gasolines and naphthas in the presence of hydrogen and a platinum-containing catalyst.

lhe increasing use of high compression, spark ignition, internal combustion engines, has brought about a growing demand for high octane number motor fuels. This has been accompanied by a decrease in the demand for gasolines possessing only moderate or low antiknock characteristics. As a result of this shift in demand, petroleum refiners are fuels such as straight-run gasolines and naphthas. A single solution to both problems lies in the conversion of low grade gasolines to those of higher grade. At least one process, thermal reforming, directed toward this end, has been used commercially. However, this particular process is limited in its ability to produce high octane number products. In addition, the reformate yield is comparatively low, particularly when a fairly high octane number product is being produced. Certain catalytic reforming processes have been proposed that are capable of producing reformate of higher octane number than can be obtained by means of thermal reforming. However, the yield-octane number relationships of toluene.

Recently, a superior reforming catalyst has been developed, said catalyst comprising platinum and alumina. This catalyst is capable number of straight-run gasolines and naphthas to values that are much higher than those that can be reached with thermal reforming and, in addition, the yieldoctane number relationship is much better than are the corresponding relationships obtained in faced with two problems, I

either thermal reforming or in the prior catalytic reforming processes. Equally important is the fact that this catalyst is substantially nonregenerative when used under proper processing conditions, and frequently can be used for months without regeneration. Inasmuch as the characteristics platinum-alumina reforming catalysts are different from those of other reforming catalysts, processes employing this type of catalyst should be different from processes uing other types in order to make the best use thereof. We have invented a process that is particularly suitable for the most economical and efficient use of these improved platinum-alumina catalysts.

In one embodiment our invention relates to an improved conversion process providing for the use of a minimum quantity of a platinum containing catalyst, and comprises heating a substantially olefin-free hydrocabon reactant containing saturated hydrocarbons and boiling approximately within the gasoline range to a con version temperature, passing the heated reactant said hydrocarbon reactant in each of the zones with a bed of said catalyst and promoting the endothermic conversion thereof, heating the hydrocarbons passing between the reaction zones to supply endothermic heat of reaction, and proportioning the catalyst among said zones to provide at least as great a quantity of catalyst in all zones cessively decreasing temperature drops in said fraction passing serially through the plurality of zones, and the last reaction zone contains a greater quantity of catalyst than the first of said plurality of zones.

In a more specific embodiment our invention relates to a process which comprises passing hydrogen and a nonolefinic hydrocarbon fraction containing naphthenes and boiling below about 425 F. through a series of at least two separate substantially adiabatic reaction zones, each containing a catalyst comprising platinum and alumina which promotes the endothermic conversion of said hydrocarbon fraction, and heatmanner that decreasing temperature drops are obtained in successive zones.

In a still more specific embodiment our inven- 3 process which comprises heathydrocarbon fraction relates to a ing a substantially olefin-free tion containing naphthenes and boiling below about 425 F. to a conversion temperature within the e. oi rom. b ut. o a out .0 E- passing the hydrocarbon fraction together with hydrogen in series flow through at least two substantially adiabatic reaction zones, containing a, catalyst comprising platinum and alumina, at reforming conditions resulting in a net endothermic heat of reaction, heating the hydrogenand hydrocarbons passing between said zones, and cor; relating the inlet temperature; to eel-Cl} Q Sal i; zones with the amount of catalyst each of, zones to obtain a temperature drop in the last zone that is less than AT/n and a temperature. drop in each of the preceding zones that is greater than AT/4n, where AT equals the, sum, of the temperature drops in each of the zones and equa s th num er oi zone h reiorohhe. 01 hr ro rh ns. e othermic the. gree o ehdet er iehr e ndin P ma ily o en. the ten of onv rsion. Un er t e e ciroo hstehoea, t hhi. hee ha s t ma eactors would bean especially suitable type teem: 12. 9% Ki i oth rm l; il r u r elaborate and costly reactor designs to provide o heat, oxehoh e. en he r ir he t n fe heeo'ome ooh. as ho s fo m t n ee s s Well as ating means, hence we prefer to, use the 3 .9 q qit mi i d ehoho Systems n the temperature. drop from. inlet to. outlet in a single oihehei e .:9i%9 .1 mey be as. much as 200 F. or more, we contemplate the use of at least two o iohohe ee or 1h t en the e e Thi arran n rr w th whee. o e ti h. tem ratu es. Pr a l n 91 eehvere h more uniform throughout the bed.

S o the Prior a t c l ic reior e an qf ormingfprocesses haye'employed two or more adiabatic reactors V in v series. with interheat ing; of. the. charge. In all, of these processes it heehe h eo r ee s e v to e r te-t e. ra lyst at regular and frequent intervals. In order when renam at liberated and protect he eiel r i rom. am o o t e rate o regenerat'ion gases that is used normally is, much greater than, the volumetric rate of the process e se h eeh e o his at n. nd h -r sul ing pressure drop problem, the more satisiactory engineering, designs have involved equal distribu tion of. the catalyst between the several reactors. Other processing'means have operated in amanner providing varying depthsv oi catalystin successive beds and equal'temperature.drops through each, bed, whereby apparatusarrangements are adapted, to reactivate a uniform rateof catalyst decline throng the successive beds, Howevenin he prese S bs a a o rece erative r forming process employing a platinumecontainne. eete t. u h as. plat num n a umina. h desi n isnot infiueho dby ene at n b ems- But, on the other hand, because of the relatively high price of the catalyst, it is necessary to desig n the plant to minimize the catalyst cost. The lowest catalyst expense results when the catalyst requirement, i el, inventory, is at a minimum for a given throughput or when the catalyst life, expressed as volume of charge stock processed per volume of catalyst, is the greatest. We have ound t he in m. ata r oh r m and the maximum catalyst life generally are obone reactor which in tu'rn resultsinmqre uniandv product quality as well as series. with reheating bedeposition of catalyst coke total; endothermic reaction tained with unequal, rather than with equal, dis* tribution of the catalyst between the various reactors. We have also found that so far as platinum-alumina catalyst is concerned, the catalyst dis r but on that. t. in the. catalyst requirements are substantially the same, as those that give maximum catalyst life.

Catalyst apportionment is the principal determinant of catalyst requirement and life, however, we also. find it practical to refer to temperature drops in the reactors in describing our process. Onereaspn for that a reactor temperature drop relatively easily determined experimentallyand; is directly related to the extent of the taking place in the reactor The total endothermic reaction in turn is related to the amount of catalyst in the reactor. another reason is that the exact proportioning in terms of relative catalyst volumes for minimore eo iromots is de d ntrea th r lat nle emp atu e and, is the ei e. lee generally applic ble. he he. n op hins, o h emp o r drone.

We hareieuhsi that here. are sev ra r qui i btain n w a1 st ioire e s-v lhe fir t. i e e ca a ys be roportion d be ween h sev ral ea o s uc a'me e ha -the mpe atur rop a h ast, r ac o s than aT/n. where/AT equals the sum of; the temperature r n a h ith r tor an n duals h ero c I t e empe ature droo. n h o e ct r s a e hon. mo specif edwill be. sqbecause, a. relatively. high conversion iseftected therein, lithe high converi n can o y b ough out n his. r ac or by a n a om er i arg amount oi ote.- yst r i ethe naeeveiocltrmhehbe l we t r et r than he h rs toef eo ah-igh onvers wh the h ah essoeh. s nlet em era ure, hr ghp t. and pre sure. are. e e t sg the sames. n. hen oine: r a tor he eby ncreas n he t tal. lv r ou remehth so or thisn nome on tha th ndothermicity per unit of, conversion, decreases with increasing convers on. Althou h th s g n rally is true, of: most endothermic, reactions, it is. es;- he io v u n h re min of, str gh er-oh gasolin or r c i n 'eot n e resenc o rgla h mra om na c talyst, which romote. o ohlvhdo her odehyd o e ti n r ons 1 also. ex the mic h roerahiha reac io s. Th o r ac on. seh th rmie hro gh ut h range oi. o ersion. no ma l he ered. t. it. is ees o; at h h h rohr rsio lyeis. be ause. the r io time. h g; o r met zat n. ncreases with conversionipr most charge. Stocks.

The-m n mum catalyst reooir irehts a ir ser real zed the tem erature ro n h as re c or s, e s t e /rrut. i doe not mean that lowest qatalyst requirement il auto,- meheolly e rea ized-if he emperatur -drop in the, final reactor is. any

nor that the temperature drop in each of the reactors preceding the last is greater than AT/4n. If it is less than this amount, the catalyst is not being used efhciently, i. e., there is too little catalyst and too small a conversion in the reactor with the low temperature drop and too much in at least one of the other reactors.

Although it is possible to effect substantial savings in catalyst requirements when using two reactors instead of one, further substantial savings are possible with three and four reactors. However, the use of more than four reactors seldom brings about a saving in catalyst proportionate to the increased outlay for equipment. Consequently, we ordinarily prefer to use either three or four reactors in our process. The data listed in the following table provide a comparison of the minimum catalyst requirements for several adiabatic reactor systems with the catalyst requirement for a single isothermal reactor operating at a temperature of 850 F. which is also the inlet temperature that was assumed for each of the adiabatic reactors. The other operating conditions were such as to give a conversion sulficient to raise the F-2 (motor method) octane number of a 40 octane number straight-run gasoline to '75 when using a catalyst comprising platinum and alumina.

TABLE I Minimum No. of Adiabatic Reactors Catalyst Requirement 1 Equivalent to an isothermal reactor.

TABLE II Reactor N o 1 2 3 4 Catalyst Distribution, Perce t' One Reactor System.. 100 Two Reactor System. 34 66 Three Reactor System 25 26 49 Four Reactor System l3 19 25 43 It will be observed that in all cases, the minimum catalyst requirement was realized with unequal amounts of catalyst in the various reactors. It should also be observed that the minimum catalyst requirement always is found in some combination of successively decreasing temperature drops in multiple adiabatic reactor systems employing interheating. This is one of the reasons that the temperature drop in the last reactor should not exceed AT/n.

The hydrocarbon stocks that may be converted in accordance with our process comprise nonolefinic hydrocarbon fractions containing saturated hydrocarbons, particularly naphthenes. By the term nonolefinic we mean substantially olefin-free, i. e., a few per cent of olefins can be present in the charge in some types of operation.

Suitable stocks include narrow boiling fractions rich in naphthenes as well as substantially pure naphthenes such as cyclohexane and methylcyclohexane. The preferred stocks are those consisting essentially of naphthenes and parafiins, although relatively minor amounts of aromatics also may be present. The naphthenes are dehydrogenated to aromatics and the parafiins are hydrocracked to lower boiling parafiins. This preferred class includes straight-run gasolines, natural gasolines, and the like. The gasoline may be a full boiling range gasoline having an initial boiling point within the range of from about 50 to about 100 F. and an end boiling point within the range of about 325 to about 425 F., or it may be a selective fraction thereof which usually will be a higher boiling fraction commonly referred to as naphtha, and generally having an initial boiling point of from about 125 to about 250 F., and an end boiling point within the range of about 350 to about 425 F. The expression straight-run gasoline fraction as used herein is intended to include both naphtha and full boiling gasolines.

The platinum-alumina catalysts that are preferred for use in our process may contain substantial amounts of platinum, but, for economic as well as for product yield and quality reasons, the platinum content usually will be within the range of from about 0.05% to about 5.0%. A particularly effective catalyst of this type contains relatively minor amounts, usually less than about 3% on a dry alumina basis, of a halogen, especially chlorine and fluorine. One method of preparing these catalysts comprises adding a suitable alkaline reagent such as ammonium hydroxide or carbonate to a salt of aluminum, such as aluminum chloride, aluminum sulfate, aluminum nitrate, and the like, in an amount sufficient to form aluminum hydroxides, which upon drying, can be converted to alumina. The halogen may be added to the resultant slurry in the form of an acid such as hydrogen fluoride or hydrogen chloride, or as a volatile salt such as ammonium fluoride or ammonium chloride. A colloidal suspension of platinic sulfide is then prepared by introducing hydrogen sulfide into an aqueous solution of chloro-platinic acid until said solution reaches a constant color, which is usually a dark brown. The resultant colloidal suspension of platinic sulfide is commingled with the aluminum hydroxide slurry at room temperature followed by stirring to obtain intimate mixing. The resulting materials are then dried at a temperature from about 200 to about 400 F. for a period of from about 4 to about 24 hour or more to form a cake. The resulting material may then be converted into pills or other shaped particles. Thereafter the catalyst may be subjected to a high temperature calcination or reduction treatment prior to use.

Reforming operations carried. out in accordance with our process in the process of platinumalumina catalysts ordinarily will be carried out employing inlet temperatures of from about 800 F. to about 950 F. At inlet temperatures much below about 800 the reaction rates are quite slow and very low space velocities must be employed to obtain appreciable conversions. At inlet temperatures much in excess of 950 F. an appreciable amount of thermal reaction takes place in the initial part of the catalyst bed accompanied by a poorer liquid recovery and more rapid catalyst deactivation.

The pressure at which our process is conducted headset.

usuaily will be within the range or rom about 50 to about 1260 pounds per s uare inch; a'vveight hourly space velocity, "hich is defined as the Weight of hydrocarbon charge per hour per weight of catalyst in the reaction zones, Within the range of from about 0.2 toabou't 4'0; 'and the amount of hydrogen charged alOng with the hy= d'rocarbons usually will be from about 0.5 to about 15 mols. per 'mol. of hydrocarbon. Y When "our process is operated at carefully correlated conditioris Within the ranges outlined above, it is surrstaritially nonre'ge'nerative' and can be operated for Weeks and even months without the necessity of regenerating the catalyst by burning the carbon therefrom.

Other latinum-containing catalysts that may be'u'sed in our process include platinum n charcoal, iplatihum'on asbestos, and platinum on bases that possess crackingi 'activi'ty such as silicaaiuniina composites. The correspondin auadiam catalysts frequently can be used in 'our proc ss;

Sulfur compounds appear to be at least ternporary poisons for platinum-alumina catalysts, consequently, thechargin'gstock should be substantially free from these 'm-ateria1s when a data .Iy'st (if this" type is employed.

The features of the recent inventior'i' will be apparent from the following description or the attached drawing which illustrates a articular ni'thdd or CGnduCtTng a reforming operation in accordance vv'ith our process.

I Referring now to the drawing; a low sulfur; Tull-boiling range straight-run gasoline which contains naphth'e'nes and paramns is" charged through line 1 containing lve' 2" and is picked up by pum 3 and passed through line 4 containingval've 5" into 'fractioriator 6. A light naphtha with an end 'p'oi'fit or about 150 F. is taken overhead from fractioriato'r B through line" 1, condenser '8, line}; arid is passed into receiver HI. The condensed naphtha in receiver it is passed into line It, .pump 12' and line I3. A portion of the light naphtha passing througri. line I3 is diverted through Ii'rie M contaihing'valve f5 and directed into the top of frelctioriatoi' B as reflux.

Heavy naphtha i'swithdrawn from fractionator 'fi' 'throug'h line it oon'tainingvalve' l1 and is joined by a hydrogen recycle streampassing through line T8. The comr'r'fiflgledstreams now through heater l9 and into reactor 21!. The niolal ratio of hydrogen to hydrocarbon the charge to reactor 0- is '621. The combined stream of h d'rO gen and hydrocarbon --flOW's in series through reactor 2t, line 2l', heater -22;.Ii'ne 23; reactor 2 1, line 25', heater '26, line 2'! and reactor 23. The catalyst comprises a composite of platinum, alumina, and fluorine, containing"0=1% platinum and 0.7% fluorine. The total amount of catalyst in the three reactors is proportioned so that 25% of it is iii-reactor 2t, 25% of it is in reactor 24', and 50% is in reactor 2-8. The inlet temperature to reactors 20; 24, and 28, is 85'0'F. The outlet temperatures for the same three reactors are approximately 751, 799,:arid 830 F. The Weight hourly space v locity is 2 and-the totalflpres'sure is 600 p. s. i. If desired; the reaction zones and heaters may be incorporated in a single vessel; separate vessels are not a necessity.

The eiiiuent' from reactor 28 is withdrawn through line zaend'c'ondenserse. and is passed through line 31 into receiver 32. In this receiver hydrogen and gaseous hydrocarbons are separatedfrom liquid hydrocarbons. Excess gas is vented through line 33 containing valve 34' and,

if desired, ma be charged to deetharii'zei 8 The remainder is recycled to the reactdr section or the-plant. it contains appreciable am'o'ui'fts of hydrogen sulfideit is passed through line -3'5 containing valve 3 6 and into hydrogen sulfide separator 31. Said separator may comprise a caustic Wash system, a diethylanolamine ethylene glycol system, or any other system thatwill effectively remove hydrogen sulfide. The effluent therefrom is passed through line 38- containing vaive 3s and into compressor terrain which it is sent through line E8" to reactor 28. If-f the recycle hydrogen streamis low in hydrogen sulfide the 1 123 separator may be bypassed via line 41- con tai'n'ing valve 42. a a

'i'heiiquid hydrocarbon in receiver 2 'arewith drawn through line {it containing valve M; are picked up by ump-t5, and are sent through here 46 containing valve'll'i into deethanizer "4'8; Ab sorption oil, prepared as hereinafter described enters the deeth'anizer near the top. Ethane and lighter gases are removed from the vessel throu lifi :9' containing valve 50. The 'deethaniz'ed liquid bottoms product is withdrawn from de 'thahi'z'er' 33 through line see. containing valve 59d, is joined by the light Straight=run naphtha from iractionator 6 passing though line t3 con-- tainingvalve 55, the combined stream is charged to stabilizer 52.

The fractionating conditions in stabilizer 52 are regulated to obtain a bottoms product of the desired vapor pressure which usuallyvvill be about 10 pounds. Light hydrocarbon such as propane together with some eateries are taken overhead from stabilizer 52 through line 53,- condenser 5 and are passed through'line 55' into receiver 56. The condensed hydrocarbons in receiver 56 are withdrawn through line 53 and a portion thereof is passed through line 59 containing valve 69, thr" "i and by means of line B2 66ntamin valve 63 is sent tothe top of stabilizer 52Where it serves as reflux. The excess light hydrocarbons are Withdrawn through line 58 con}- tai'rii'ng valve 57 and are'sen't to storage or are otherwise disposed'o'f. I

The stabilized hydrocarbons are withdrawn from vessel 52 through line 6a containing v'a-lve '65 and are sent to storage. This stream constitutes a major product of the'process; A portion or" the stream flowing through line 62, is passed throughline 58 containing valve 5'! and is directed into stripper 68. The vapor pressure of this stream is reduced inorder to make a suitable absorption oil from it by removing light hydrocarbons overhead as vapors through line 59 conraining valve 10 and passing them intostabilizer '52. The stabilized hydrocarbons, which may have-a vapor pressureof 1 or Zpounds, are then withdrawn from the'bottom of stabilizer EB-and are'passed through line H containing valve T2; p'ump i-S and valve 1 itothe top or deetha-nizer-AB;

I-f' a high er' boiling naphtha is'to be charged to our process, prefractionatcr 6 and the auxiliary equipment 'used-in' conjunction therewith may be eliminated; Thereactors'sho'uld not be made'of "iron hles's they contain-a suitable'liner; because iron has a deleterious effect upon the platinum: alumina catalyst. The catalystneed not necessarily"be'disposed'asfixed'beds in the reactors in allty'pe's of operations; it can, for example, be presentin a finely divided form ahdthe'hydr'o gen and hydrocarbons passed upwardly therethrough in a fluidized-fiXed-be'd ty'pe of operation;

An alterhati've method of operation comprises passing a portion of the recycle hydrogen stream, which contains an appreciable quantity of low boiling hydrocarbons, to absorber 18 and therein using a portion of the bottoms of fractionatcr 6 as a lean absorber oil. The rich absorption oil is returned to fractionator 6. The liquid hydrocarbons in receiver 32 are then passed, together with the light naphtha from fractionator 6, to stabilizer '52. In this embodiment stripper 68 may be eliminated. The overhead product from stabilizer 52 may or may not be returned to the absorber as desired.

From the foregoing specification it can be seen that we have provdcd an improved substantially non-regenerative method for the reforming of hydrocarbons, particularly in the presence of platinum-alumina catalysts. Further, we are not concerned with providing a switch or regenerating operation and by means of our process the most eflicient use and the favorable characteristics of this type of catalyst are utilized to the fullest extent, with the result that higher yields of higher octane number-products are produced with a smaller amount of catalyst and at a longer like than would be possible with conventional methods of operation.

We claim as our invention:

1. In an endothermic, substantially non-regenerative catalytic process for the reforming of a substantially olefin-free, normally liquid gasoline fraction in contact With a platinum-containing catalyst, the improved method of operation providing for the economical utilization and minimum quantity of the platinum-containing catalyst, which comprises passing the gasoline fraction through a series of at least two reaction zones containing separate beds of said catalyst, proportioning the catalyst among said zones so that each zone of the series succeeding the first zone contains a quantity of catalyst at least equal to that in the first zone of the series and the last zone of the series contains a greater quantity of catalyst than each preceding zone, heating the gasoline fraction to reforming temperature prior to its introduction to each of said zones, and. correlating the inlet temperature of the heated gasoline fraction to each zone with the amount of catalyst therein to obtain a temperature drop in said last zone that is less than AT/n and a temperature drop in each preceding zone of the se ries that is greater than AT/4n, where AT equals the sum of the temperature drops in said zones and 'n equals the number of zones in the series.

2. In an endothermic, substantially non-regenerative catalytic process for the reforming of a substantially olefin-free, normally liquid gasoline fraction in contact with a platinum-containing catalyst, the improved method of operation providing for the economical utilization and minimum quantity of the platinum-containing catalyst, which comprises passing the gasoline fraction through a series of at least three reaction zones containing separate beds of said catalyst, proportioning the catalyst among said zones so that each zone of the series intermediate the first and the last contains a quantity of catalyst at least equal to that in the first zone and the last zone of the series contains a greater quantity of catalyst than each preceding zone, heating the gasoline fraction to reforming temperature prior to its introduction to said first zone and reheating it to reforming temperature between successive zones of the series, and cor-- relating the inlet temperature of the heated gasoline fraction to each zone with the amount of catalyst therein to obtain a temperature drop in said last zone that is less than AT/n and a temperature drop in each preceding zone of the series that is greater than AT/n, where AT equals the sum of the temperature drops in said zones and n equals the number of zones in the series.

3. In an endothermic, substantially non-regenerative catalytic process for the reforming of a substantially olefin-free, normally liquid gasoline fraction in contact with a platinum-containing catalyst, the improved method of operation providing for the economical utilization and minimum quantity of the platinum-containing catalyst, which comprises passing the gasoline fraction through a series of three reaction zones containing separate beds of said catalyst, proportioning the catalyst among said zones so that the second zone of the series contains a quantity of catalyst at least equal to that in the first zone of the series and the third zone of the series contains a greater quantity of catalyst than said second zone, heating the gasoline fraction to reforming temperature prior to its introduction to said first zone and reheating it to reforming temperature between the first and second zones and between the second and third zones, and correlating the inlet temperature of the heated gasoline fraction to each zone with the amount of catalyst therein to obtain a temperature drop in said third zone that is less than AT/3 and a temperature drop in each of said first and second zones that is greater than AT/ 12, where AT equals the sum of the temperature drops in said zones.

4. In an endothermic, substantially non-regenerative catalytic process for the reforming of a substantially olefin-free, normally liquid gasoline fraction in contact with a platinum-containing catalyst, the improved method of operation providing for the economical utilization and minimum quantity of the platinum-containing catalyst, which comprises passing the gasoline fraction through a series of three reaction zones containing separate beds of said catalyst, proportioning the catalyst among said zones so that the first and second zones of the series contain approximately equal quantities of catalyst and the third zone of the series contains a greater quantity of catalyst than each of said first and second zones, heating the gasoline fraction to reforming temperature prior to its introduction to each of said zones, and correlating the inlet temperature of the heated gasoline fraction to each zone with the amount of catalyst therein to obtain a temperature drop in said third zone that is less than AT/3 and a temperature drop in each of said first and second zones that is greater than AT/12, where AT equals the sum of the temperature drops in said zones.

5. The method of claim 1 further characterized in that said reaction zones are maintained under substantially adiabatic conditions.

CHARLES V. BERGER. DAVID D. HANSEN.

References Cited in the file of this paten UNITED STATES PATENTS Y Number Name Date 2,366,567 Schultz Jan. 2, 1945 2,411,726 Holroyd et al Nov. 26, 1946 2,479,110 Haensel Aug. 16, 1949 

1. IN AN ENDOTHERMIC, SUBSTANTIALLY NON-REGENERATIVE CATALYTIC PROCESS FOR THE REFORMING OF A SUBSTANTIALLY OLEFIN-FREE, NORMALLY LIQUID GASOLINE FRACTION IN CONTACT WITH A PLATINUM-CONTAINING CATALYST, THE IMPOVED METHOD OF OPERATION PROVIDING FOR THE ECONOMICAL UTILIZATION AND MINIMUM QUALITY OF THE PLATINUM-CONTAINING CATALYST, WHICH COMPRISES PASSING THE GASOLINE FRAC TION THROUGH A SERIES OF AT LEAST TOW REACTION ZONES CONTAINING SEPARATE BEDS OF SAID CATALYST PORPORTIONING THE CATALYST AMONG SAID ZONES SO THAT EACH ZONE OF THE SERIES SUCCEEDING THE FIRST ZONE CONTAINS A QUANTITY OF CATALYST AT LEAST EQUAL TO THAT IN THE FIRST ZONE OF THE SERIES AND THE LAST ZONE OF THE SERIES CONTAINS A GREATER QUANTITY OF CATALYST THAN EACH PRECEDING ZONE, HEATING THE GASOLINE FRACTION TO REFORMING TEMPERATURE PRIOR TO ITS INTRODUCTION TO EACH OF SAID ZONES, AND CORRELATING THE INLET TEMPERATURE OF THE HEATED GASOLINE FRACTION TO EACH ZONE WITH THE AMOUNT OF CATALYST THEREIN TO OBTAIN A TEMPERATURE DROP IN SAID LAST ZONE THAT IS LESS THAN $T/N AND A TEMPERATURE DROP IN EACH PRECEDING ZONE OF THE SERIES THAT IS GREATER THAN $T/4N, WHERE $T EQUALS THE SUM OF THE TEMPERATURE DROPE IN SAID ZONES AND N EQUALS THE NUMBER OF ZONES IN THE SERIES. 